status-desktop/ui/shared/xss.js

/**
 * NOTICE:
 *
 * Most this code was copied from https://github.com/leizongmin/js-xss and slightly modifed
 * to work with JavaScript resource loading in QML.
 */

var defaultCSSFilter = new FilterCSS();

var DEFAULT = {
  whiteList: getDefaultWhiteList(),
  getDefaultWhiteList,
  onTag,
  onIgnoreTag,
  onTagAttr,
  onIgnoreTagAttr,
  safeAttrValue,
  escapeHtml,
  escapeQuote,
  unescapeQuote,
  escapeHtmlEntities,
  escapeDangerHtml5Entities,
  clearNonPrintableCharacter,
  friendlyAttrValue,
  escapeAttrValue,
  onIgnoreTagStripAll,
  StripTagBody,
  stripCommentTag ,
  stripBlankChar,
  cssFilter: defaultCSSFilter,
  getDefaultCSSWhiteList,
}

/**
 * shallow copy
 *
 * @param {Object} obj
 * @return {Object}
 */
function shallowCopyObject(obj) {
  var ret = {};
  for (var i in obj) {
    ret[i] = obj[i];
  }
  return ret;
}


var _ = {
  indexOf: function(arr, item) {
    var i, j;
    if (Array.prototype.indexOf) {
      return arr.indexOf(item);
    }
    for (i = 0, j = arr.length; i < j; i++) {
      if (arr[i] === item) {
        return i;
      }
    }
    return -1;
  },
  forEach: function(arr, fn, scope) {
    var i, j;
    if (Array.prototype.forEach) {
      return arr.forEach(fn, scope);
    }
    for (i = 0, j = arr.length; i < j; i++) {
      fn.call(scope, arr[i], i, arr);
    }
  },
  trim: function(str) {
    if (String.prototype.trim) {
      return str.trim();
    }
    return str.replace(/(^\s*)|(\s*$)/g, "");
  },
  spaceIndex: function(str) {
    var reg = /\s|\n|\t/;
    var match = reg.exec(str);
    return match ? match.index : -1;
  }
};

function filterXSS(html, options) {
  var xss = new FilterXSS(options);
  return xss.process(html);
}

function onAttr (name, value, options) {
  // do nothing
}

function onIgnoreAttr (name, value, options) {
  // do nothing
}

/**
 * FilterXSS class
 *
 * @param {Object} options
 *        whiteList, onTag, onTagAttr, onIgnoreTag,
 *        onIgnoreTagAttr, safeAttrValue, escapeHtml
 *        stripIgnoreTagBody, allowCommentTag, stripBlankChar
 *        css{whiteList, onAttr, onIgnoreAttr} `css=false` means don't use `cssfilter`
 */
function FilterXSS(options) {
  options = shallowCopyObject(options || {});

  if (options.stripIgnoreTag) {
    if (options.onIgnoreTag) {
      console.error(
        'Notes: cannot use these two options "stripIgnoreTag" and "onIgnoreTag" at the same time'
      );
    }
    options.onIgnoreTag = onIgnoreTagStripAll;
  }

  options.whiteList = options.whiteList || getDefaultWhiteList();
  options.onTag = options.onTag || onTag;
  options.onTagAttr = options.onTagAttr || onTagAttr;
  options.onIgnoreTag = options.onIgnoreTag || onIgnoreTag;
  options.onIgnoreTagAttr = options.onIgnoreTagAttr || onIgnoreTagAttr;
  options.safeAttrValue = options.safeAttrValue || safeAttrValue;
  options.escapeHtml = options.escapeHtml || escapeHtml;
  this.options = options;

  if (options.css === false) {
    this.cssFilter = false;
  } else {
    options.css = options.css || {};
    this.cssFilter = new FilterCSS(options.css);
  }
}

/**
 * start process and returns result
 *
 * @param {String} html
 * @return {String}
 */
FilterXSS.prototype.process = function(html) {
  // compatible with the input
  html = html || "";
  html = html.toString();
  if (!html) return "";

  var me = this;
  var options = me.options;
  var whiteList = options.whiteList;
  var onTag = options.onTag;
  var onIgnoreTag = options.onIgnoreTag;
  var onTagAttr = options.onTagAttr;
  var onIgnoreTagAttr = options.onIgnoreTagAttr;
  var safeAttrValue = options.safeAttrValue;
  var escapeHtml = options.escapeHtml;
  var cssFilter = me.cssFilter;

  // remove invisible characters
  if (options.stripBlankChar) {
    html = stripBlankChar(html);
  }

  // remove html comments
  if (!options.allowCommentTag) {
    html = stripCommentTag(html);
  }

  // if enable stripIgnoreTagBody
  var stripIgnoreTagBody = false;
  if (options.stripIgnoreTagBody) {
    var stripIgnoreTagBody = StripTagBody(
      options.stripIgnoreTagBody,
      onIgnoreTag
    );
    onIgnoreTag = stripIgnoreTagBody.onIgnoreTag;
  }

  var retHtml = parseTag(
    html,
    function(sourcePosition, position, tag, html, isClosing) {
      var info = {
        sourcePosition: sourcePosition,
        position: position,
        isClosing: isClosing,
        isWhite: whiteList.hasOwnProperty(tag)
      };

      // call `onTag()`
      var ret = onTag(tag, html, info);
      if (!isNull(ret)) return ret;

      if (info.isWhite) {
        if (info.isClosing) {
          return "</" + tag + ">";
        }

        var attrs = getAttrs(html);
        var whiteAttrList = whiteList[tag];
        var attrsHtml = parseAttr(attrs.html, function(name, value) {
          // call `onTagAttr()`
          var isWhiteAttr = _.indexOf(whiteAttrList, name) !== -1;
          var ret = onTagAttr(tag, name, value, isWhiteAttr);
          if (!isNull(ret)) return ret;

          if (isWhiteAttr) {
            // call `safeAttrValue()`
            value = safeAttrValue(tag, name, value, cssFilter);
            if (value) {
              return name + '="' + value + '"';
            } else {
              return name;
            }
          } else {
            // call `onIgnoreTagAttr()`
            var ret = onIgnoreTagAttr(tag, name, value, isWhiteAttr);
            if (!isNull(ret)) return ret;
            return;
          }
        });

        // build new tag html
        var html = "<" + tag;
        if (attrsHtml) html += " " + attrsHtml;
        if (attrs.closing) html += " /";
        html += ">";
        return html;
      } else {
        // call `onIgnoreTag()`
        var ret = onIgnoreTag(tag, html, info);
        if (!isNull(ret)) return ret;
        return escapeHtml(html);
      }
    },
    escapeHtml
  );

  // if enable stripIgnoreTagBody
  if (stripIgnoreTagBody) {
    retHtml = stripIgnoreTagBody.remove(retHtml);
  }

  return retHtml;
};


function getDefaultWhiteList() {
  return {
    a: ["target", "href", "title", "class"],
    abbr: ["title"],
    address: [],
    area: ["shape", "coords", "href", "alt"],
    article: [],
    aside: [],
    audio: ["autoplay", "controls", "loop", "preload", "src"],
    b: [],
    bdi: ["dir"],
    bdo: ["dir"],
    big: [],
    blockquote: ["cite"],
    br: [],
    caption: [],
    center: [],
    cite: [],
    code: [],
    col: ["align", "valign", "span", "width"],
    colgroup: ["align", "valign", "span", "width"],
    dd: [],
    del: ["datetime"],
    details: ["open"],
    div: [],
    dl: [],
    dt: [],
    em: [],
    font: ["color", "size", "face"],
    footer: [],
    h1: [],
    h2: [],
    h3: [],
    h4: [],
    h5: [],
    h6: [],
    header: [],
    hr: [],
    i: [],
    img: ["src", "alt", "title", "width", "height"],
    ins: ["datetime"],
    li: [],
    mark: [],
    nav: [],
    ol: [],
    p: [],
    pre: [],
    s: [],
    section: [],
    small: [],
    span: [],
    sub: [],
    sup: [],
    strong: [],
    table: ["width", "height", "border", "bgcolor", "cellspacing", "cellpadding", "class"],
    tbody: ["align", "valign"],
    td: ["width", "bgcolor", "rowspan", "colspan", "align", "valign", "class"],
    tfoot: ["align", "valign"],
    th: ["width", "rowspan", "colspan", "align", "valign"],
    thead: ["align", "valign"],
    tr: ["rowspan", "align", "valign"],
    tt: [],
    u: [],
    ul: [],
    video: ["autoplay", "controls", "loop", "preload", "src", "height", "width"]
  };
}

function getDefaultCSSWhiteList () {
  // 白名单值说明：
  // true: 允许该属性
  // Function: function (val) { } 返回true表示允许该属性，其他值均表示不允许
  // RegExp: regexp.test(val) 返回true表示允许该属性，其他值均表示不允许
  // 除上面列出的值外均表示不允许
  var whiteList = {};

  whiteList['align-content'] = false; // default: auto
  whiteList['align-items'] = false; // default: auto
  whiteList['align-self'] = false; // default: auto
  whiteList['alignment-adjust'] = false; // default: auto
  whiteList['alignment-baseline'] = false; // default: baseline
  whiteList['all'] = false; // default: depending on individual properties
  whiteList['anchor-point'] = false; // default: none
  whiteList['animation'] = false; // default: depending on individual properties
  whiteList['animation-delay'] = false; // default: 0
  whiteList['animation-direction'] = false; // default: normal
  whiteList['animation-duration'] = false; // default: 0
  whiteList['animation-fill-mode'] = false; // default: none
  whiteList['animation-iteration-count'] = false; // default: 1
  whiteList['animation-name'] = false; // default: none
  whiteList['animation-play-state'] = false; // default: running
  whiteList['animation-timing-function'] = false; // default: ease
  whiteList['azimuth'] = false; // default: center
  whiteList['backface-visibility'] = false; // default: visible
  whiteList['background'] = true; // default: depending on individual properties
  whiteList['background-attachment'] = true; // default: scroll
  whiteList['background-clip'] = true; // default: border-box
  whiteList['background-color'] = true; // default: transparent
  whiteList['background-image'] = true; // default: none
  whiteList['background-origin'] = true; // default: padding-box
  whiteList['background-position'] = true; // default: 0% 0%
  whiteList['background-repeat'] = true; // default: repeat
  whiteList['background-size'] = true; // default: auto
  whiteList['baseline-shift'] = false; // default: baseline
  whiteList['binding'] = false; // default: none
  whiteList['bleed'] = false; // default: 6pt
  whiteList['bookmark-label'] = false; // default: content()
  whiteList['bookmark-level'] = false; // default: none
  whiteList['bookmark-state'] = false; // default: open
  whiteList['border'] = true; // default: depending on individual properties
  whiteList['border-bottom'] = true; // default: depending on individual properties
  whiteList['border-bottom-color'] = true; // default: current color
  whiteList['border-bottom-left-radius'] = true; // default: 0
  whiteList['border-bottom-right-radius'] = true; // default: 0
  whiteList['border-bottom-style'] = true; // default: none
  whiteList['border-bottom-width'] = true; // default: medium
  whiteList['border-collapse'] = true; // default: separate
  whiteList['border-color'] = true; // default: depending on individual properties
  whiteList['border-image'] = true; // default: none
  whiteList['border-image-outset'] = true; // default: 0
  whiteList['border-image-repeat'] = true; // default: stretch
  whiteList['border-image-slice'] = true; // default: 100%
  whiteList['border-image-source'] = true; // default: none
  whiteList['border-image-width'] = true; // default: 1
  whiteList['border-left'] = true; // default: depending on individual properties
  whiteList['border-left-color'] = true; // default: current color
  whiteList['border-left-style'] = true; // default: none
  whiteList['border-left-width'] = true; // default: medium
  whiteList['border-radius'] = true; // default: 0
  whiteList['border-right'] = true; // default: depending on individual properties
  whiteList['border-right-color'] = true; // default: current color
  whiteList['border-right-style'] = true; // default: none
  whiteList['border-right-width'] = true; // default: medium
  whiteList['border-spacing'] = true; // default: 0
  whiteList['border-style'] = true; // default: depending on individual properties
  whiteList['border-top'] = true; // default: depending on individual properties
  whiteList['border-top-color'] = true; // default: current color
  whiteList['border-top-left-radius'] = true; // default: 0
  whiteList['border-top-right-radius'] = true; // default: 0
  whiteList['border-top-style'] = true; // default: none
  whiteList['border-top-width'] = true; // default: medium
  whiteList['border-width'] = true; // default: depending on individual properties
  whiteList['bottom'] = false; // default: auto
  whiteList['box-decoration-break'] = true; // default: slice
  whiteList['box-shadow'] = true; // default: none
  whiteList['box-sizing'] = true; // default: content-box
  whiteList['box-snap'] = true; // default: none
  whiteList['box-suppress'] = true; // default: show
  whiteList['break-after'] = true; // default: auto
  whiteList['break-before'] = true; // default: auto
  whiteList['break-inside'] = true; // default: auto
  whiteList['caption-side'] = false; // default: top
  whiteList['chains'] = false; // default: none
  whiteList['clear'] = true; // default: none
  whiteList['clip'] = false; // default: auto
  whiteList['clip-path'] = false; // default: none
  whiteList['clip-rule'] = false; // default: nonzero
  whiteList['color'] = true; // default: implementation dependent
  whiteList['color-interpolation-filters'] = true; // default: auto
  whiteList['column-count'] = false; // default: auto
  whiteList['column-fill'] = false; // default: balance
  whiteList['column-gap'] = false; // default: normal
  whiteList['column-rule'] = false; // default: depending on individual properties
  whiteList['column-rule-color'] = false; // default: current color
  whiteList['column-rule-style'] = false; // default: medium
  whiteList['column-rule-width'] = false; // default: medium
  whiteList['column-span'] = false; // default: none
  whiteList['column-width'] = false; // default: auto
  whiteList['columns'] = false; // default: depending on individual properties
  whiteList['contain'] = false; // default: none
  whiteList['content'] = false; // default: normal
  whiteList['counter-increment'] = false; // default: none
  whiteList['counter-reset'] = false; // default: none
  whiteList['counter-set'] = false; // default: none
  whiteList['crop'] = false; // default: auto
  whiteList['cue'] = false; // default: depending on individual properties
  whiteList['cue-after'] = false; // default: none
  whiteList['cue-before'] = false; // default: none
  whiteList['cursor'] = false; // default: auto
  whiteList['direction'] = false; // default: ltr
  whiteList['display'] = true; // default: depending on individual properties
  whiteList['display-inside'] = true; // default: auto
  whiteList['display-list'] = true; // default: none
  whiteList['display-outside'] = true; // default: inline-level
  whiteList['dominant-baseline'] = false; // default: auto
  whiteList['elevation'] = false; // default: level
  whiteList['empty-cells'] = false; // default: show
  whiteList['filter'] = false; // default: none
  whiteList['flex'] = false; // default: depending on individual properties
  whiteList['flex-basis'] = false; // default: auto
  whiteList['flex-direction'] = false; // default: row
  whiteList['flex-flow'] = false; // default: depending on individual properties
  whiteList['flex-grow'] = false; // default: 0
  whiteList['flex-shrink'] = false; // default: 1
  whiteList['flex-wrap'] = false; // default: nowrap
  whiteList['float'] = false; // default: none
  whiteList['float-offset'] = false; // default: 0 0
  whiteList['flood-color'] = false; // default: black
  whiteList['flood-opacity'] = false; // default: 1
  whiteList['flow-from'] = false; // default: none
  whiteList['flow-into'] = false; // default: none
  whiteList['font'] = true; // default: depending on individual properties
  whiteList['font-family'] = true; // default: implementation dependent
  whiteList['font-feature-settings'] = true; // default: normal
  whiteList['font-kerning'] = true; // default: auto
  whiteList['font-language-override'] = true; // default: normal
  whiteList['font-size'] = true; // default: medium
  whiteList['font-size-adjust'] = true; // default: none
  whiteList['font-stretch'] = true; // default: normal
  whiteList['font-style'] = true; // default: normal
  whiteList['font-synthesis'] = true; // default: weight style
  whiteList['font-variant'] = true; // default: normal
  whiteList['font-variant-alternates'] = true; // default: normal
  whiteList['font-variant-caps'] = true; // default: normal
  whiteList['font-variant-east-asian'] = true; // default: normal
  whiteList['font-variant-ligatures'] = true; // default: normal
  whiteList['font-variant-numeric'] = true; // default: normal
  whiteList['font-variant-position'] = true; // default: normal
  whiteList['font-weight'] = true; // default: normal
  whiteList['grid'] = false; // default: depending on individual properties
  whiteList['grid-area'] = false; // default: depending on individual properties
  whiteList['grid-auto-columns'] = false; // default: auto
  whiteList['grid-auto-flow'] = false; // default: none
  whiteList['grid-auto-rows'] = false; // default: auto
  whiteList['grid-column'] = false; // default: depending on individual properties
  whiteList['grid-column-end'] = false; // default: auto
  whiteList['grid-column-start'] = false; // default: auto
  whiteList['grid-row'] = false; // default: depending on individual properties
  whiteList['grid-row-end'] = false; // default: auto
  whiteList['grid-row-start'] = false; // default: auto
  whiteList['grid-template'] = false; // default: depending on individual properties
  whiteList['grid-template-areas'] = false; // default: none
  whiteList['grid-template-columns'] = false; // default: none
  whiteList['grid-template-rows'] = false; // default: none
  whiteList['hanging-punctuation'] = false; // default: none
  whiteList['height'] = true; // default: auto
  whiteList['hyphens'] = false; // default: manual
  whiteList['icon'] = false; // default: auto
  whiteList['image-orientation'] = false; // default: auto
  whiteList['image-resolution'] = false; // default: normal
  whiteList['ime-mode'] = false; // default: auto
  whiteList['initial-letters'] = false; // default: normal
  whiteList['inline-box-align'] = false; // default: last
  whiteList['justify-content'] = false; // default: auto
  whiteList['justify-items'] = false; // default: auto
  whiteList['justify-self'] = false; // default: auto
  whiteList['left'] = false; // default: auto
  whiteList['letter-spacing'] = true; // default: normal
  whiteList['lighting-color'] = true; // default: white
  whiteList['line-box-contain'] = false; // default: block inline replaced
  whiteList['line-break'] = false; // default: auto
  whiteList['line-grid'] = false; // default: match-parent
  whiteList['line-height'] = false; // default: normal
  whiteList['line-snap'] = false; // default: none
  whiteList['line-stacking'] = false; // default: depending on individual properties
  whiteList['line-stacking-ruby'] = false; // default: exclude-ruby
  whiteList['line-stacking-shift'] = false; // default: consider-shifts
  whiteList['line-stacking-strategy'] = false; // default: inline-line-height
  whiteList['list-style'] = true; // default: depending on individual properties
  whiteList['list-style-image'] = true; // default: none
  whiteList['list-style-position'] = true; // default: outside
  whiteList['list-style-type'] = true; // default: disc
  whiteList['margin'] = true; // default: depending on individual properties
  whiteList['margin-bottom'] = true; // default: 0
  whiteList['margin-left'] = true; // default: 0
  whiteList['margin-right'] = true; // default: 0
  whiteList['margin-top'] = true; // default: 0
  whiteList['marker-offset'] = false; // default: auto
  whiteList['marker-side'] = false; // default: list-item
  whiteList['marks'] = false; // default: none
  whiteList['mask'] = false; // default: border-box
  whiteList['mask-box'] = false; // default: see individual properties
  whiteList['mask-box-outset'] = false; // default: 0
  whiteList['mask-box-repeat'] = false; // default: stretch
  whiteList['mask-box-slice'] = false; // default: 0 fill
  whiteList['mask-box-source'] = false; // default: none
  whiteList['mask-box-width'] = false; // default: auto
  whiteList['mask-clip'] = false; // default: border-box
  whiteList['mask-image'] = false; // default: none
  whiteList['mask-origin'] = false; // default: border-box
  whiteList['mask-position'] = false; // default: center
  whiteList['mask-repeat'] = false; // default: no-repeat
  whiteList['mask-size'] = false; // default: border-box
  whiteList['mask-source-type'] = false; // default: auto
  whiteList['mask-type'] = false; // default: luminance
  whiteList['max-height'] = true; // default: none
  whiteList['max-lines'] = false; // default: none
  whiteList['max-width'] = true; // default: none
  whiteList['min-height'] = true; // default: 0
  whiteList['min-width'] = true; // default: 0
  whiteList['move-to'] = false; // default: normal
  whiteList['nav-down'] = false; // default: auto
  whiteList['nav-index'] = false; // default: auto
  whiteList['nav-left'] = false; // default: auto
  whiteList['nav-right'] = false; // default: auto
  whiteList['nav-up'] = false; // default: auto
  whiteList['object-fit'] = false; // default: fill
  whiteList['object-position'] = false; // default: 50% 50%
  whiteList['opacity'] = false; // default: 1
  whiteList['order'] = false; // default: 0
  whiteList['orphans'] = false; // default: 2
  whiteList['outline'] = false; // default: depending on individual properties
  whiteList['outline-color'] = false; // default: invert
  whiteList['outline-offset'] = false; // default: 0
  whiteList['outline-style'] = false; // default: none
  whiteList['outline-width'] = false; // default: medium
  whiteList['overflow'] = false; // default: depending on individual properties
  whiteList['overflow-wrap'] = false; // default: normal
  whiteList['overflow-x'] = false; // default: visible
  whiteList['overflow-y'] = false; // default: visible
  whiteList['padding'] = true; // default: depending on individual properties
  whiteList['padding-bottom'] = true; // default: 0
  whiteList['padding-left'] = true; // default: 0
  whiteList['padding-right'] = true; // default: 0
  whiteList['padding-top'] = true; // default: 0
  whiteList['page'] = false; // default: auto
  whiteList['page-break-after'] = false; // default: auto
  whiteList['page-break-before'] = false; // default: auto
  whiteList['page-break-inside'] = false; // default: auto
  whiteList['page-policy'] = false; // default: start
  whiteList['pause'] = false; // default: implementation dependent
  whiteList['pause-after'] = false; // default: implementation dependent
  whiteList['pause-before'] = false; // default: implementation dependent
  whiteList['perspective'] = false; // default: none
  whiteList['perspective-origin'] = false; // default: 50% 50%
  whiteList['pitch'] = false; // default: medium
  whiteList['pitch-range'] = false; // default: 50
  whiteList['play-during'] = false; // default: auto
  whiteList['position'] = false; // default: static
  whiteList['presentation-level'] = false; // default: 0
  whiteList['quotes'] = false; // default: text
  whiteList['region-fragment'] = false; // default: auto
  whiteList['resize'] = false; // default: none
  whiteList['rest'] = false; // default: depending on individual properties
  whiteList['rest-after'] = false; // default: none
  whiteList['rest-before'] = false; // default: none
  whiteList['richness'] = false; // default: 50
  whiteList['right'] = false; // default: auto
  whiteList['rotation'] = false; // default: 0
  whiteList['rotation-point'] = false; // default: 50% 50%
  whiteList['ruby-align'] = false; // default: auto
  whiteList['ruby-merge'] = false; // default: separate
  whiteList['ruby-position'] = false; // default: before
  whiteList['shape-image-threshold'] = false; // default: 0.0
  whiteList['shape-outside'] = false; // default: none
  whiteList['shape-margin'] = false; // default: 0
  whiteList['size'] = false; // default: auto
  whiteList['speak'] = false; // default: auto
  whiteList['speak-as'] = false; // default: normal
  whiteList['speak-header'] = false; // default: once
  whiteList['speak-numeral'] = false; // default: continuous
  whiteList['speak-punctuation'] = false; // default: none
  whiteList['speech-rate'] = false; // default: medium
  whiteList['stress'] = false; // default: 50
  whiteList['string-set'] = false; // default: none
  whiteList['tab-size'] = false; // default: 8
  whiteList['table-layout'] = false; // default: auto
  whiteList['text-align'] = true; // default: start
  whiteList['text-align-last'] = true; // default: auto
  whiteList['text-combine-upright'] = true; // default: none
  whiteList['text-decoration'] = true; // default: none
  whiteList['text-decoration-color'] = true; // default: currentColor
  whiteList['text-decoration-line'] = true; // default: none
  whiteList['text-decoration-skip'] = true; // default: objects
  whiteList['text-decoration-style'] = true; // default: solid
  whiteList['text-emphasis'] = true; // default: depending on individual properties
  whiteList['text-emphasis-color'] = true; // default: currentColor
  whiteList['text-emphasis-position'] = true; // default: over right
  whiteList['text-emphasis-style'] = true; // default: none
  whiteList['text-height'] = true; // default: auto
  whiteList['text-indent'] = true; // default: 0
  whiteList['text-justify'] = true; // default: auto
  whiteList['text-orientation'] = true; // default: mixed
  whiteList['text-overflow'] = true; // default: clip
  whiteList['text-shadow'] = true; // default: none
  whiteList['text-space-collapse'] = true; // default: collapse
  whiteList['text-transform'] = true; // default: none
  whiteList['text-underline-position'] = true; // default: auto
  whiteList['text-wrap'] = true; // default: normal
  whiteList['top'] = false; // default: auto
  whiteList['transform'] = false; // default: none
  whiteList['transform-origin'] = false; // default: 50% 50% 0
  whiteList['transform-style'] = false; // default: flat
  whiteList['transition'] = false; // default: depending on individual properties
  whiteList['transition-delay'] = false; // default: 0s
  whiteList['transition-duration'] = false; // default: 0s
  whiteList['transition-property'] = false; // default: all
  whiteList['transition-timing-function'] = false; // default: ease
  whiteList['unicode-bidi'] = false; // default: normal
  whiteList['vertical-align'] = false; // default: baseline
  whiteList['visibility'] = false; // default: visible
  whiteList['voice-balance'] = false; // default: center
  whiteList['voice-duration'] = false; // default: auto
  whiteList['voice-family'] = false; // default: implementation dependent
  whiteList['voice-pitch'] = false; // default: medium
  whiteList['voice-range'] = false; // default: medium
  whiteList['voice-rate'] = false; // default: normal
  whiteList['voice-stress'] = false; // default: normal
  whiteList['voice-volume'] = false; // default: medium
  whiteList['volume'] = false; // default: medium
  whiteList['white-space'] = false; // default: normal
  whiteList['widows'] = false; // default: 2
  whiteList['width'] = true; // default: auto
  whiteList['will-change'] = false; // default: auto
  whiteList['word-break'] = true; // default: normal
  whiteList['word-spacing'] = true; // default: normal
  whiteList['word-wrap'] = true; // default: normal
  whiteList['wrap-flow'] = false; // default: auto
  whiteList['wrap-through'] = false; // default: wrap
  whiteList['writing-mode'] = false; // default: horizontal-tb
  whiteList['z-index'] = false; // default: auto

  return whiteList;
}


/**
 * 创建CSS过滤器
 *
 * @param {Object} options
 *   - {Object} whiteList
 *   - {Function} onAttr
 *   - {Function} onIgnoreAttr
 *   - {Function} safeAttrValue
 */
function FilterCSS (options) {
  options = shallowCopyObject(options || {});
  options.whiteList = options.whiteList || getDefaultWhiteList()
  options.onAttr = options.onAttr || onAttr;
  options.onIgnoreAttr = options.onIgnoreAttr || onIgnoreAttr;
  options.safeAttrValue = options.safeAttrValue || safeAttrValue;
  this.options = options;
}

FilterCSS.prototype.process = function (css) {
  // 兼容各种奇葩输入
  css = css || '';
  css = css.toString();
  if (!css) return '';

  var me = this;
  var options = me.options;
  var whiteList = options.whiteList;
  var onAttr = options.onAttr;
  var onIgnoreAttr = options.onIgnoreAttr;
  var safeAttrValue = options.safeAttrValue;

  var retCSS = parseStyle(css, function (sourcePosition, position, name, value, source) {

    var check = whiteList[name];
    var isWhite = false;
    if (check === true) isWhite = check;
    else if (typeof check === 'function') isWhite = check(value);
    else if (check instanceof RegExp) isWhite = check.test(value);
    if (isWhite !== true) isWhite = false;

    // 如果过滤后 value 为空则直接忽略
    value = safeAttrValue(name, value);
    if (!value) return;

    var opts = {
      position: position,
      sourcePosition: sourcePosition,
      source: source,
      isWhite: isWhite
    };

    if (isWhite) {

      var ret = onAttr(name, value, opts);
      if (isNull(ret)) {
        return name + ':' + value;
      } else {
        return ret;
      }

    } else {

      var ret = onIgnoreAttr(name, value, opts);
      if (!isNull(ret)) {
        return ret;
      }

    }
  });

  return retCSS;
};

/**
 * default onTag function
 *
 * @param {String} tag
 * @param {String} html
 * @param {Object} options
 * @return {String}
 */
function onTag(tag, html, options) {
  // do nothing
}

/**
 * default onIgnoreTag function
 *
 * @param {String} tag
 * @param {String} html
 * @param {Object} options
 * @return {String}
 */
function onIgnoreTag(tag, html, options) {
  // do nothing
}

/**
 * default onTagAttr function
 *
 * @param {String} tag
 * @param {String} name
 * @param {String} value
 * @return {String}
 */
function onTagAttr(tag, name, value) {
  // do nothing
}

/**
 * default onIgnoreTagAttr function
 *
 * @param {String} tag
 * @param {String} name
 * @param {String} value
 * @return {String}
 */
function onIgnoreTagAttr(tag, name, value) {
  // do nothing
}

/**
 * default escapeHtml function
 *
 * @param {String} html
 */
function escapeHtml(html) {
  return html.replace(REGEXP_LT, "&lt;").replace(REGEXP_GT, "&gt;");
}

/**
 * default safeAttrValue function
 *
 * @param {String} tag
 * @param {String} name
 * @param {String} value
 * @param {Object} cssFilter
 * @return {String}
 */
function safeAttrValue(tag, name, value, cssFilter) {
  // unescape attribute value firstly
  value = friendlyAttrValue(value);

  if (name === "href" || name === "src") {
    // filter `href` and `src` attribute
    // only allow the value that starts with `http://` | `https://` | `mailto:` | `/` | `#`
    value = _.trim(value);
    if (value === "#") return "#";
    if (
      !(
        value.substr(0, 7) === "http://" ||
        value.substr(0, 8) === "https://" ||
        value.substr(0, 7) === "mailto:" ||
        value.substr(0, 4) === "tel:" ||
        value.substr(0, 11) === "data:image/" ||
        value.substr(0, 6) === "ftp://" ||
        value.substr(0, 2) === "./" ||
        value.substr(0, 3) === "../" ||
        value[0] === "#" ||
        value[0] === "/"
      )
    ) {
      return "";
    }
  } else if (name === "background") {
    // filter `background` attribute (maybe no use)
    // `javascript:`
    REGEXP_DEFAULT_ON_TAG_ATTR_4.lastIndex = 0;
    if (REGEXP_DEFAULT_ON_TAG_ATTR_4.test(value)) {
      return "";
    }
  } else if (name === "style") {
    // `expression()`
    REGEXP_DEFAULT_ON_TAG_ATTR_7.lastIndex = 0;
    if (REGEXP_DEFAULT_ON_TAG_ATTR_7.test(value)) {
      return "";
    }
    // `url()`
    REGEXP_DEFAULT_ON_TAG_ATTR_8.lastIndex = 0;
    if (REGEXP_DEFAULT_ON_TAG_ATTR_8.test(value)) {
      REGEXP_DEFAULT_ON_TAG_ATTR_4.lastIndex = 0;
      if (REGEXP_DEFAULT_ON_TAG_ATTR_4.test(value)) {
        return "";
      }
    }
    if (cssFilter !== false) {
      cssFilter = cssFilter || defaultCSSFilter;
      value = cssFilter.process(value);
    }
  }

  // escape `<>"` before returns
  value = escapeAttrValue(value);
  return value;
}

// RegExp list
var REGEXP_LT = /</g;
var REGEXP_GT = />/g;
var REGEXP_QUOTE = /"/g;
var REGEXP_QUOTE_2 = /&quot;/g;
var REGEXP_ATTR_VALUE_1 = /&#([a-zA-Z0-9]*);?/gim;
var REGEXP_ATTR_VALUE_COLON = /&colon;?/gim;
var REGEXP_ATTR_VALUE_NEWLINE = /&newline;?/gim;
var REGEXP_DEFAULT_ON_TAG_ATTR_3 = /\/\*|\*\//gm;
var REGEXP_DEFAULT_ON_TAG_ATTR_4 = /((j\s*a\s*v\s*a|v\s*b|l\s*i\s*v\s*e)\s*s\s*c\s*r\s*i\s*p\s*t\s*|m\s*o\s*c\s*h\s*a)\:/gi;
var REGEXP_DEFAULT_ON_TAG_ATTR_5 = /^[\s"'`]*(d\s*a\s*t\s*a\s*)\:/gi;
var REGEXP_DEFAULT_ON_TAG_ATTR_6 = /^[\s"'`]*(d\s*a\s*t\s*a\s*)\:\s*image\//gi;
var REGEXP_DEFAULT_ON_TAG_ATTR_7 = /e\s*x\s*p\s*r\s*e\s*s\s*s\s*i\s*o\s*n\s*\(.*/gi;
var REGEXP_DEFAULT_ON_TAG_ATTR_8 = /u\s*r\s*l\s*\(.*/gi;

/**
 * escape doube quote
 *
 * @param {String} str
 * @return {String} str
 */
function escapeQuote(str) {
  return str.replace(REGEXP_QUOTE, "&quot;");
}

/**
 * unescape double quote
 *
 * @param {String} str
 * @return {String} str
 */
function unescapeQuote(str) {
  return str.replace(REGEXP_QUOTE_2, '"');
}

/**
 * escape html entities
 *
 * @param {String} str
 * @return {String}
 */
function escapeHtmlEntities(str) {
  return str.replace(REGEXP_ATTR_VALUE_1, function replaceUnicode(str, code) {
    return code[0] === "x" || code[0] === "X"
      ? String.fromCharCode(parseInt(code.substr(1), 16))
      : String.fromCharCode(parseInt(code, 10));
  });
}

/**
 * escape html5 new danger entities
 *
 * @param {String} str
 * @return {String}
 */
function escapeDangerHtml5Entities(str) {
  return str
    .replace(REGEXP_ATTR_VALUE_COLON, ":")
    .replace(REGEXP_ATTR_VALUE_NEWLINE, " ");
}

/**
 * clear nonprintable characters
 *
 * @param {String} str
 * @return {String}
 */
function clearNonPrintableCharacter(str) {
  var str2 = "";
  for (var i = 0, len = str.length; i < len; i++) {
    str2 += str.charCodeAt(i) < 32 ? " " : str.charAt(i);
  }
  return _.trim(str2);
}

/**
 * get friendly attribute value
 *
 * @param {String} str
 * @return {String}
 */
function friendlyAttrValue(str) {
  str = unescapeQuote(str);
  str = escapeHtmlEntities(str);
  str = escapeDangerHtml5Entities(str);
  str = clearNonPrintableCharacter(str);
  return str;
}

/**
 * unescape attribute value
 *
 * @param {String} str
 * @return {String}
 */
function escapeAttrValue(str) {
  str = escapeQuote(str);
  str = escapeHtml(str);
  return str;
}

/**
 * `onIgnoreTag` function for removing all the tags that are not in whitelist
 */
function onIgnoreTagStripAll() {
  return "";
}

/**
 * remove tag body
 * specify a `tags` list, if the tag is not in the `tags` list then process by the specify function (optional)
 *
 * @param {array} tags
 * @param {function} next
 */
function StripTagBody(tags, next) {
  if (typeof next !== "function") {
    next = function() {};
  }

  var isRemoveAllTag = !Array.isArray(tags);
  function isRemoveTag(tag) {
    if (isRemoveAllTag) return true;
    return _.indexOf(tags, tag) !== -1;
  }

  var removeList = [];
  var posStart = false;

  return {
    onIgnoreTag: function(tag, html, options) {
      if (isRemoveTag(tag)) {
        if (options.isClosing) {
          var ret = "[/removed]";
          var end = options.position + ret.length;
          removeList.push([
            posStart !== false ? posStart : options.position,
            end
          ]);
          posStart = false;
          return ret;
        } else {
          if (!posStart) {
            posStart = options.position;
          }
          return "[removed]";
        }
      } else {
        return next(tag, html, options);
      }
    },
    remove: function(html) {
      var rethtml = "";
      var lastPos = 0;
      _.forEach(removeList, function(pos) {
        rethtml += html.slice(lastPos, pos[0]);
        lastPos = pos[1];
      });
      rethtml += html.slice(lastPos);
      return rethtml;
    }
  };
}

/**
 * remove html comments
 *
 * @param {String} html
 * @return {String}
 */
function stripCommentTag(html) {
  return html.replace(STRIP_COMMENT_TAG_REGEXP, "");
}
var STRIP_COMMENT_TAG_REGEXP = /<!--[\s\S]*?-->/g;

/**
 * remove invisible characters
 *
 * @param {String} html
 * @return {String}
 */
function stripBlankChar(html) {
  var chars = html.split("");
  chars = chars.filter(function(char) {
    var c = char.charCodeAt(0);
    if (c === 127) return false;
    if (c <= 31) {
      if (c === 10 || c === 13) return true;
      return false;
    }
    return true;
  });
  return chars.join("");
}


/**
 * get tag name
 *
 * @param {String} html e.g. '<a hef="#">'
 * @return {String}
 */
function getTagName(html) {
  var i = _.spaceIndex(html);
  if (i === -1) {
    var tagName = html.slice(1, -1);
  } else {
    var tagName = html.slice(1, i + 1);
  }
  tagName = _.trim(tagName).toLowerCase();
  if (tagName.slice(0, 1) === "/") tagName = tagName.slice(1);
  if (tagName.slice(-1) === "/") tagName = tagName.slice(0, -1);
  return tagName;
}

/**
 * is close tag?
 *
 * @param {String} html 如：'<a hef="#">'
 * @return {Boolean}
 */
function isClosing(html) {
  return html.slice(0, 2) === "</";
}

/**
 * parse input html and returns processed html
 *
 * @param {String} html
 * @param {Function} onTag e.g. function (sourcePosition, position, tag, html, isClosing)
 * @param {Function} escapeHtml
 * @return {String}
 */
function parseTag(html, onTag, escapeHtml) {
  "use strict";

  var rethtml = "";
  var lastPos = 0;
  var tagStart = false;
  var quoteStart = false;
  var currentPos = 0;
  var len = html.length;
  var currentTagName = "";
  var currentHtml = "";

  for (currentPos = 0; currentPos < len; currentPos++) {
    var c = html.charAt(currentPos);
    if (tagStart === false) {
      if (c === "<") {
        tagStart = currentPos;
        continue;
      }
    } else {
      if (quoteStart === false) {
        if (c === "<") {
          rethtml += escapeHtml(html.slice(lastPos, currentPos));
          tagStart = currentPos;
          lastPos = currentPos;
          continue;
        }
        if (c === ">") {
          rethtml += escapeHtml(html.slice(lastPos, tagStart));
          currentHtml = html.slice(tagStart, currentPos + 1);
          currentTagName = getTagName(currentHtml);
          rethtml += onTag(
            tagStart,
            rethtml.length,
            currentTagName,
            currentHtml,
            isClosing(currentHtml)
          );
          lastPos = currentPos + 1;
          tagStart = false;
          continue;
        }
        if ((c === '"' || c === "'") && html.charAt(currentPos - 1) === "=") {
          quoteStart = c;
          continue;
        }
      } else {
        if (c === quoteStart) {
          quoteStart = false;
          continue;
        }
      }
    }
  }
  if (lastPos < html.length) {
    rethtml += escapeHtml(html.substr(lastPos));
  }

  return rethtml;
}

var REGEXP_ILLEGAL_ATTR_NAME = /[^a-zA-Z0-9_:\.\-]/gim;

/**
 * parse input attributes and returns processed attributes
 *
 * @param {String} html e.g. `href="#" target="_blank"`
 * @param {Function} onAttr e.g. `function (name, value)`
 * @return {String}
 */
function parseAttr(html, onAttr) {
  "use strict";

  var lastPos = 0;
  var retAttrs = [];
  var tmpName = false;
  var len = html.length;

  function addAttr(name, value) {
    name = _.trim(name);
    name = name.replace(REGEXP_ILLEGAL_ATTR_NAME, "").toLowerCase();
    if (name.length < 1) return;
    var ret = onAttr(name, value || "");
    if (ret) retAttrs.push(ret);
  }

  // 逐个分析字符
  for (var i = 0; i < len; i++) {
    var c = html.charAt(i);
    var v, j;
    if (tmpName === false && c === "=") {
      tmpName = html.slice(lastPos, i);
      lastPos = i + 1;
      continue;
    }
    if (tmpName !== false) {
      if (
        i === lastPos &&
        (c === '"' || c === "'") &&
        html.charAt(i - 1) === "="
      ) {
        j = html.indexOf(c, i + 1);
        if (j === -1) {
          break;
        } else {
          v = _.trim(html.slice(lastPos + 1, j));
          addAttr(tmpName, v);
          tmpName = false;
          i = j;
          lastPos = i + 1;
          continue;
        }
      }
    }
    if (/\s|\n|\t/.test(c)) {
      html = html.replace(/\s|\n|\t/g, " ");
      if (tmpName === false) {
        j = findNextEqual(html, i);
        if (j === -1) {
          v = _.trim(html.slice(lastPos, i));
          addAttr(v);
          tmpName = false;
          lastPos = i + 1;
          continue;
        } else {
          i = j - 1;
          continue;
        }
      } else {
        j = findBeforeEqual(html, i - 1);
        if (j === -1) {
          v = _.trim(html.slice(lastPos, i));
          v = stripQuoteWrap(v);
          addAttr(tmpName, v);
          tmpName = false;
          lastPos = i + 1;
          continue;
        } else {
          continue;
        }
      }
    }
  }

  if (lastPos < html.length) {
    if (tmpName === false) {
      addAttr(html.slice(lastPos));
    } else {
      addAttr(tmpName, stripQuoteWrap(_.trim(html.slice(lastPos))));
    }
  }

  return _.trim(retAttrs.join(" "));
}

function findNextEqual(str, i) {
  for (; i < str.length; i++) {
    var c = str[i];
    if (c === " ") continue;
    if (c === "=") return i;
    return -1;
  }
}

function findBeforeEqual(str, i) {
  for (; i > 0; i--) {
    var c = str[i];
    if (c === " ") continue;
    if (c === "=") return i;
    return -1;
  }
}

function isQuoteWrapString(text) {
  if (
    (text[0] === '"' && text[text.length - 1] === '"') ||
    (text[0] === "'" && text[text.length - 1] === "'")
  ) {
    return true;
  } else {
    return false;
  }
}

function stripQuoteWrap(text) {
  if (isQuoteWrapString(text)) {
    return text.substr(1, text.length - 2);
  } else {
    return text;
  }
}


/**
 * returns `true` if the input value is `undefined` or `null`
 *
 * @param {Object} obj
 * @return {Boolean}
 */
function isNull(obj) {
  return obj === undefined || obj === null;
}

/**
 * get attributes for a tag
 *
 * @param {String} html
 * @return {Object}
 *   - {String} html
 *   - {Boolean} closing
 */
function getAttrs(html) {
  var i = _.spaceIndex(html);
  if (i === -1) {
    return {
      html: "",
      closing: html[html.length - 2] === "/"
    };
  }
  html = _.trim(html.slice(i + 1, -1));
  var isClosing = html[html.length - 1] === "/";
  if (isClosing) html = _.trim(html.slice(0, -1));
  return {
    html: html,
    closing: isClosing
  };
}